In the usual construction of buildings, doors are hung in openings formed by boxing-in the thickness of the surrounding walls. While previously, carpenters would typically "build-in" a door by shimming and/or planing the opening to the appropriate size, shape and degree of squareness necessary to accommodate a door and then building a finished frame in the opening, it has been found more advantageous to employ prefabricated door frames. Such frames generally present a better appearance than individually built frames and also are more cost-effective insofar as the use of skilled labor, and long periods of time are not required to hang a door. Furthermore, prefabricated door frames may be manufactured from durable materials such as metals or polymeric composites and thereby provide strength not attainable with individually built door frames. For this reason, the construction trades have turned very strongly to the use of prefabricated door frames.
Such frames may be utilized in a pre-hung or non-pre-hung mode. In a pre-hung mode, the door frame is completely assembled and includes the door mounted therein. In such instances the builder will simply insert the appropriate frame in a door opening, affix the frame and attach any necessary hardware. In a non- pre-hung mode, the door frame is supplied either fully assembled or in components which are assembled into the opening and a door is subsequently affixed thereto.
Regardless of whether a pre-hung or non-pre- hung mode of construction is employed, it is generally desirable that prefabricated door frames be adjustable so as to accommodate variations in wall thickness resultant from irregularities in construction materials or techniques, as well as to accommodate openings in walls of various nominal dimensions. Frequently in the construction of buildings lumber, drywall or similar materials will be found to be slightly oversized or undersized; similarly, a door opening may be slightly out of plumb, or it may be of non-uniform width (i.e., slightly tapered). Consequently, the thickness or width of the opening may be greater at one end thereof than at the other. If door frames of fixed size were employed in such situations, they could not accommodate the irregularity. Furthermore, it is desirable to have adjustable door frames adapted to accommodate a wide variety of nominal wall thicknesses so as to obviate the necessity of warehousing numerous sizes.
It is further desirable that any such adjustable door frame be strong so as to provide sufficient security for use in mounting entry doors. Additionally, such frames should present an aesthetically attractive appearance, be of low cost and be easy to fabricate and install.
Previously, numerous designs of door frame assemblies have been fabricated which allow for some small degree of adjustability, typically up to one-half inch, so as to accommodate slight variations in wall thicknesses. Such door frame assemblies are generally manufactured as two-piece assemblies having a crimped portion adapted to retain a sliding second portion therein. While such amount of adjustability is useful, it frequently is not sufficient insofar as variations in wall size of greater than one-half inch can readily occur over a 7 or 8 foot length of a door opening. Furthermore, as previously noted, such frame designs cannot accommodate a variety of wall sizes.
In response to the need for a door frame having a greater range of adjustability, various designs have been developed. One group of adjustable door frames employs a two-piece frame assembly and has various slider or ratchet assemblies which hold the two portions in alignment while allowing for expansion or contraction thereof. For example, U.S. Pat. Nos. 2,853,161 and 4,395,855 depict slide assemblies whereas U.S. Pat. No. 3,906,671 illustrates a ratcheted assembly. While such designs do allow for adjustability, they typically are expensive to fabricate insofar as precision alignment of the sliders or other attachment mechanism is required over an extensive length of door frame during its manufacture. Additionally, use of such door frames is complicated by the necessity of previously aligning the mating portions of the frame members. The general fragility of such precise members necessitates careful handling during manufacturing, shipping and use and frequently results in ruined product.
Accordingly, it is desirable that any such adjustable door frame not require precision manufacturing steps or necessitate precise alignment during use and be rugged enough to withstand normal handling at a construction site. Disclosed in U.S. Pat. No. 3,884,003 is a two-piece door frame assembly in which a plurality of clips welded to one member of the frame retain the second portion thereof. This design eliminates some of the problems of the aforementioned frames. However, welding of the clips occasions other problems insofar as welding is an relatively expensive process to fixture, and the welded points tend to become potential rust centers. Additionally, the use of a welding process precludes manufacture of the frame from prepainted metal stock, use of which significantly reduces production cost, and eliminates time and expense associated with field painting. Another problem with the welding of attachment clips is that the welding process of necessity heats the material, thereby reducing temper and gripping efficacy of the clips. For these reasons, it is desirable to eliminate the use of a welding process in the fabrication of such frames.
U.S. Pat. No. 3,788,019 discloses an adjustable door frame system which relies upon a plurality of clips nailed to the opening in the wall to retain the door frame assembly and allow for adjustability thereof. While such clips do overcome problems occasioned by welding, their use is difficult insofar as the clips must be properly shimmed and attached to the door opening in precise alignment so as to properly retain the frame. Additionally, the frame, once assembled, cannot be removed and cannot be repositioned without removal and repositioning of the shimmed clips.
Accordingly, it will be appreciated that, despite the various designs for adjustable door frame assemblies, there is still is a need for an assembly which is simple and rapid to use, does not require precise positioning of components thereof, is capable cf withstanding rough shipping conditions, is economical to manufacture and does not necessitate welding steps.
The present invention provides for an adjustable door frame capable of accommodating a wide range of door opening thicknesses and capable of accommodating significant variations within the nominal thickness. The door frame assembly of the present invention is fabricated as a two-part assembly held together by a plurality of spring clips of unique design. The clips are retained internally of the frame assembly, may be repositioned if required, and their use eliminates the need for precise alignment of the two portions of the frame assembly. Elimination of welding steps allows for the use of economical and attractive prepainted stock material and eliminates weld damage which may result in rust. The frame assemblies of the present invention may be utilized in either a pre-hung or non-pre-hung mode and may be quickly installed and removed, without the need for shimming. These and other advantages of the present invention will be readily apparent from the drawings, descriptions and claims which follow.